In a rotary coupling for feeding a gaseous or liquid pressurized medium from a first to a second machine part, which are rotatable with respect to each other, the first machine part can be at least one feed piston formed as a spring supported hollow piston and a sliding shoe mounted between the feed piston and the second machine part.
One disadvantage of such rotary couplings, particularly for high pressure use, is that during the rotary motion one of the sealing surfaces must rub against the other. In order to keep the energy consumption which results from this friction as low as possible and in order to remove the heat generated as quickly and effectively as possible so that neither the sealing surfaces nor the medium being fed through under pressure are overheated, one frequently permits the introduction of the fluid medium under pressure into the gap between the sealing surfaces gliding past or sliding over each other. This hydrostatic compensation is taught in German Pat. No. 34 44 850.
This approach is not sufficient, however, for high pressure rotary couplings at high rotation speed and/or peripheral speed when the rotary coupling runs "dry", that is, no pressurized fluid medium is present.
Particularly in rotary couplings in which a high sliding speed is present as a result of a greater rotation speed or greater diameter of the contacting surfaces satisfactory results can only be attained when permanent pressurizing and/or lubricating and cooling means are present.